Disclaimer: Wizards of the Coast urges adventurers to remember that not all rock creatures are earth elementals. A talking rock that controls boulders is a galeb duhr. A talking rock wearing jewelry is a dao. A silent rock that's resistant to non-adamantine weapons is a stone golem. A rock with wings is a gargoyle. A rock without a K is a giant bird. A rock that sits there and does nothing could be just a rock or a balor disguised by an illusion. In all cases, proceed with caution.
— Disclaimer on the Princes of the Apocalypse module credits page, Dungeons & Dragons